Heat exchangers with catalytic combustion



March 24, 1959 A. P. J. HUET HEAT EXCHANGERS WITH CATALYTIC COMBUSTION Filed Nov. 29, 1955 INVENTOR. ANDRE PHILIPPE JEAN HUET A77 RNEY U tcd ttes Pat HEAT EXCHANGERS WITH CATALYTIC COMBUSTION Andr Philippe Jean Huet, Paris, France Application November 29, 1955, Serial No. 549,824 Claims priority, application France December 7, 1954 4 Claims. (Cl. 122-4) changer may, in addition, he of different diameters. The

characteristic feature common to these arrangements resides in the fact that the passages which are provided between the rows of tubes, and which are traversed by the external fluid circulating in the exchanger, have a wall contour such as to subject the current passing therethrough to changes of direction and to variations of section which cause changes of pressure and velocity in the fluid, with the final result of ensuring optimum sweeping of the surface of the tubes by said external fluid, and thence leading to improvement of the exchange of heat, with low loss of pressure.

It is found that heat exchangers of this type are equally adapted to the flow of a gas, certain constituents of which necessarily give rise, by contact with catalysts, to an exothermic chemical reaction, from which it is precisely of advantage to recover as completely and as rapidly as possible the heat liberated thereby. In fact, the catalysts ensuring combustion are generally disposed on supports and the catalytic reaction is the better, the more eflicient the sweeping of the surface of the support by the gases.

The subject matter of the present invention is accordingly a heat exchanger in which a catalytic combustion of the gas supplying its heat to the exchanger is carried out.

To this end, the supports for the catalysts may be tubes made of any suitable material traversed by a fluid absorbing the heat from the support, and said tubes will be given a section and arrangement which will be those of the heat exchangers referred to hereinabove.

Alternatively, the catalyst supports, which are generally in the form of bars, will be mingled with the tubes of a heat exchanger in order to obtain, in the long run, by combining the section of the bars and that of the tubes of the heat exchanger, the above indicated forms of passages.

In the case in which, as has already been proposed by applicant, the catalyst substance is deposited directly on the tubes of the exchanger, the invention relates to the fact that said tubes carrying the catalytic body are disposed in such a manner as to ensure an optimum sweeping eflect on the surface of the tubes.

If desired, the intervals between the rows of tubes may be such as to increase or diminish in proportion as the fluid flows inthe catalytic combustion exchanger; and that the spacing between the tubes may be likewise such as to increase or diminish in each row, in such a manner as to adapt the flow properties of the heat exchanger to the volume and to the pressure of the gases resulting from the gradient of temperatures produced by the catalytic combustion of said gases.

Moreover, instead of equipping all the tubes of the heat exchanger with a catalytic substance, only those which are, for example, the first to be reached by the external fluid may be so equipped, the other tubes being considered as the tubes of an ordinary exchanger.

The foregoing arrangements are applicable in the case of the fluid circulating externally of the tubes. It is likewise envisaged, in accordance with the present invention, that they may be applied in a heat exchanger to the fluid circulating inside the tubes, in the case where, for example, a hot fluid circulates inside tubes bathed in an external fluid to be heated. The catalyst will then be disposed either inside the tubes of the exchanger, for example on deflectors or bodies situated inside the tube and which improve the transmission of heat by causing stripping away of the limit layer of the fluid on the internal surface of the tubes, or else at the inlet of the tubes. In the case in which the inlets of said tubes are provided with helicoidal ribs intended to facilitate at the same time admission of the fluid to the interior of the tubes and turbulence of the fluid inside the tube, the catalyst will be conveniently disposed on said helicoidal ribs.

The invention will be further described with reference to the attached drawings which are given by way of example, and in which:

Figure 1 shows in cross-section a heat exchanger having tangentially finned tubes arranged in regular rows.

Figure 2 shows in section a heat exchanger having smooth rods and diametrically finned tubes disposed in regular and alternate rows,

Figure 3 is a heat exchanger having smooth tubes and tubes with tangential fins disposed in a staggered arrangement.

Figure 4 is a longitudinal section of an exchanger tube containing a deflector.

Figure 5 shows in longitudinal section the inlet of. an exchanger tube equipped with helicoidal ribs.

In the exchanger arrangements which were referred to at the beginning of this description there were provided passages between the vertical rows" of A A, B--B, C-C horizontal tubes shown in section in Figure 1, said passages being traversed by the external fluid in the general direction of flow F and being-such that the current is subjected to changes in direction and, on the other hand, to variations in section passing from the narrow section I-l--H to the widened section I-I, and so on.

The catalytic combustion exchanger ,in accordance with the present invention is constructed, as shown in Figure 1, with the aid of tubes .a having tangential fins b ar ranged in regular horizontal rows indicated at X and Z. In order to ensure the catalytic combustion of constituents of the fluid F, catalysts are carried by supports forming part of the exchanger. Said supports may, for example, be solid rods or bars which are given a tangential fin section and which are shown at c. In Figure 1, the support bars c are shown arranged in a row Y, alternating with the rows XZ of exchanger tubes. In this way, the licking of the surfaces of the support bars 0 by the flow of external fluid F is ensured to the maximum extent, and the catalytic reaction which must take place is ensured to the utmost, while the heat emitted by this combustion is absorbed in the tubes a.

In Figure 2 there has been shown in regular rows an alternation of diametrally finned tubes d with smooth bars of cylindrical section e serving as supports for the catalyst. It is seen that the passages constructed between the columns AA,BB'likewise have widened sections 'and 'narrow sections, while 'the inclination, directed now in one direction, now in another, of the diametral fins of the tubes d ensures that the total cylindrical surface'ofthesupport 'bars c'isswept by the flux F.

The support bars e for the catalysts may themselves be tubular, and traversed by a fluid exchanging its heat withtheexternal'fluid F in which a catalytised reaction takes place. This arrangement has been shown in Figurei3, inwhich can'be seen the bars e given the form -of smooth tubes and disposed in staggered rows Y, be-

tween'the rows XZ of tubes with tangential fins, likewise 'in staggered arrangement. The same internal fluid or a different fluid canflow through the supports e and the tube withtangentialffins a.

The cooling 'of the supports a for the catalysts is 'ensuredin more immediate fashion if'they are traversed by a cooling fluid and, under these conditions, instead of using supports resistant to'high temperature, it is poss'ible to use metal support .tubes.

'It is evident that many combinations may be envisaged as between the devices which have just been described by way of example. 'The tubes may be in regular rows, in regularorirregular staggered rows, alternating with bars, or tubes for supporting the catalysts and diametrically or tangentially finned tubes, in the same row, or in different rows. The support bars, or tubes may have anysection. It is not necessary that the supports for the catalysts c, e, e shouldhave the same radius as the tubes proper of the exchanger. If, for example, they'have a smaller radius, the rows of tubes will peri odically be brought closer together,-so as to obtain the sweeping effects indicated hereinabove, and the intervals between the rows of tubes will be different.

The internal combustion heat exchanger forming the 'subject of the present invention may likewise provide for internal combustion of the fluid circulating inside the tubes a of the exchanger. For example, there may be provided in the'interior of said tubes, as shown in Figure 4, deflectors or baflles g which have the effect of creating changes of direction and variation in velocity and pressure in the internal fluid circulating in the direction of the arrows G. When the 'fluid G contains gases which may give rise to a catalytic combustion, the catalytic' substances capable of producing this reaction will 'be disposed on the baffles g.

It is also possible to provide the tubes a of the exchanger with an inlet h of generally truncated-conical shape and having helicoidal ribs i intended to impart to the 'fluid penetrating in the direction of the arrow G into theinterior of the tube aa gyratory movement.

This arrangement .is shown in Figure 5, and in the case of aninternal combustion exchanger, according to the invention, the catalytic bodies maybe disposed on the wall of .the cone at the inlet and/or on the ribs i at the inlet, and the catalytic action will be promoted by the gyrating movement assumed by the fluid.

It is obvious that modifications in detail may be made in the carrying out of this invention, without thereby departing from its scope as defined by the claims.

What I claimis:

l. Ina heat exchanger for indirect heat exchange between .a first combustible fluid and a second fluid, said exchanger including a zone for the flow of the combustible fluid from an inlet end to an outlet end of said zone, in combination, a plurality of tubes adapted to have the second fluid flow therethrough, said tubes being disposed in parallel relationship across said zone with their axes at right angles to the direction of flow between said inlet "end 'and 'said outlet-end, said parallel tubes being disposed in parallel rows containing at least two tubes in each row and defining parallel channels for the flow of-said combustible fluid through said zone in contact :with:said :tubes, :and'means defining cylindrical surfaces having axes parallel to the axes of said tubes and disposed adjacent said tubes in said rows to be engaged by the combustible fluid in flowing through said channels, each of said tubes having a cylindrical surface adjacent thereto and each tube being formed with blades extending outwardly from its periphery, said blades being disposed in relation to the adjacent cylindrical surfaces with the plane of each blade substantially tangential to the next adjacent cylindrical surface, said cylindrical surfaces supporting at least one catalyst body adapted to produce an exothermic catalytic reaction in the combustible fluid flowing through said zone in contact with said cylindrical surfaces and with the surfaces of said tubes, said catalyst body being wholly supported on said cylindrical surfaces and said plates onsaid tubes serving to direct said combustible fluid ontosaidfree cylindrical surfaces for contact with said catalyst body.

2. In a heat exchanger for indirect heat exchange between a first combustible fluid and a second fluid, said exchanger including a'zone for the flow of'the combustible fluid from an inlet end to an outlet end of said zone, in combination, a plurality of tubes adapted to have the second fluid flow therethrough, said tubesbeing disposed in parallel relationship across said zone with their axes at right angles to the direction of flow between said inlet end and said outlet end, said parallel tubes being disposed in parallel rows containing at least two tubes in each row and defining parallel channels for the flow of said combustible fluid through said zone in contact with said tubes, and tubular means defining cylindrical surfaces having axes parallel to the axes of said tubes 'and disposed adjacent said tubes in said rows to be engaged by the combustible fluid in flowing through said channels, each of said tubes having a cylindrical surface adjacent thereto and each tube being formed with blades extending outwardly from its periphery, said blades being disposed in relation to the adjacent cylindrical surfaces with the plane of each blade substantially tangential to the next adjacent cylindrical surface, said cylindrical surfaces supporting at least one catalyst body adapted to producc'an exothermic catalytic reaction in the combustible fluid flowing through said zone in contact with said cylindrical surfaces and with the surfaces of said tubes, said catalyst body being wholly supported on said cylindrical surfaces and said plates on said tubes serving to direct said combustible fluid onto said free cylindrical surfaces for contact with said catalyst body.

3. In a heat exchanger for indirect heat exchange between a first combustible fluid and a second fluid, said exchanger including a zone for the flow of the combustible fluid from an inlet end to an outlet end of said zone, in combination, a plurality of tubes adapted to have the second fluid flow therethrough, said tubes being disposed in parallel relationship across said zone with their axes at right angles to the direction of flow between said inlet end and said outlet end, said parallel tubes being disposed in parallel rows containing at least two tubes in each row and defining parallel channels for the flow of said combustible fluid through said zone in contact with said tubes, and tubular means defining cylindrical surfaces having axes parallel to the axes of said tubes and disposed adjacent said tubes in said rows to be engaged by the combustible fluid in flowing through said channels. said tubular means being adapted to have said second fluid flow therethrough, each of said tubes having a cylindrical surface adjacent thereto and each tube being formed with blades extending outwardly from its periphery, said blades being disposed in relation to the adjacent cylindrical surfaces with the plane of each blade substantially tangential to the next adjacent cylindrical surface, said cylindrical surfaces supporting at least one catalyst body adapted to produce an exothermic catalytic reaction in the combustible fluid flowing through said .zone in contact .with said cylindrical surfaces and with the surfaces of said tubes, said catalyst body being wholly supported on said cylindrical surfaces and said plates on said tubes serving to direct said combustible fluid onto said free cylindrical surfaces 13]. contact with said catalyst body.

4. In a heat exchanger for indirect heat exchange between a first combustible fluid and a second fluid, said exchanger including a zone for the flow of the combustible fluid from an inlet end to an outlet end of said zone, in combination, a plurality of tubes adapted to have the second fluid flow therethrough, said tubes being disposed in parallel relationship across said zone with their axes at right angles to the direction of flow between said inlet end and said outlet end, said parallel tubes being disposed in parallel rows containing at least two tubes in each row and defining parallel channels for the flow of said combustible fluid through said zone in contact with said tubes, and tubular means defining cylindrical surfaces having axes parallel to the axes of said tubes and disposed adjacent said tubes in said rows to be engaged by the combustible fluid in flowing through said channels, the diameter of said tubular means being different from the diameter of said tubes, each of said tubes having a cylindrical surface adjacent thereto and each tube being formed with blades extending outwardly from its periphery, said blades being disposed in relation to the adjacent cylindrical surfaces with the plane of each blade substantially tangential to the next adjacent cylindrical surface, said cylindrical surfaces supporting at least one catalyst body adapted to produce an exothermic catalytic reaction in the combustible fluid flowing through said zone in contact with said cylindrical surfaces and with the surfaces of said tubes, said catalyst body being wholly supported on said cylindrical surfaces and said plates on said tubes serving to direct said combustible fluid onto said free cylindrical surfaces for contact with said catalyst body.

References Cited in the file of this patent UNITED STATES PATENTS 1,043,580 Eldred Nov. 5, 1912 1,904,216 Forward Apr. 18, 1933 2,163,591 Deverall June 27, 1939 2,293,946 Payne Aug. 25, 1942 2,412,809 Harlow Dec. 17, 1946 2,431,228 Burgess Nov. 18, 1947 2,444,908 Bailey July 13, 1948 2,578,136 Huet Dec. 11, 1951 2,778,610 Bruegger Jan. 22, 1957 OTHER REFERENCES Oil and Gas Journal, vol. 53, June 7, 1954, pages 99 to 101 and 109 TN 860; 039. 

